Fix tests on CI

[rettinghaus]

It seems like test only run properly for owners of the repo. Tests are green on my fork, but they fail here for PRs.

[ColeDCrawford]

For a while there was an issue on my fork when the workflow attempted to publish benchmark results to a non-existent Github Pages site, but I fixed that. I am also experiencing failing tests at the "Pytest comment" step during PRs from forks. Reruns of the CI workflow use "the privileges of the actor who initially triggered the workflow, not the privileges of the actor who initiated the re-run" (docs) so that's not a manual option either.

We could try changing the workflow to use the fork's context (where contributors have permission) by running it on pull_request_target? That seems less than ideal. Otherwise I think we would need to move the Pytest coverage comment step. @aweakley any thoughts?

[aweakley]

Could we skip the pytest comment step unless it's the main branch maybe?
Also the combined coverage report is a bit confusing https://github.com/ixc/python-edtf/actions/runs/10395598114/job/28787984733#step:9:16 because it lists the files from the two sets of tests separately rather than properly combining them.